Method of transmitting and receiving device-to-device discovery signal

ABSTRACT

A method to transmit and receive a device-to-device (D2D) discovery signal method is disclosed. The D2D discovery signal method operates using currently defined discovery signals as well as novel discovery signals, such as discovery signals employing a PUCCH-based uplink signal, an SRS-based demodulation and reference signal, or a single tone-based beacon signal. Under the D2D discovery signal method, an enhanced base station (eNB) configures the D2D discovery signal to both the transmitter (TX) user equipment (UE) and the receiver (RX) UE, then activates the D2D discovery signal to the TX and RX UEs, such that D2D signal transmission can thereafter occur from either the eNB or the TX UE, and monitored by the RX UE. Once the eNB deactivates the D2D discovery signal, D2D transmissions between UEs cease. Transmissions to configure, activate, and deactivate the D2D discovery signal can be unicast, multicast, or broadcast.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Number 61/734,323, filed on Dec. 6, 2012.

TECHNICAL FIELD

This application relates to methods for configuring and activating or deactivating a device-to-device discovery signal.

BACKGROUND

Proximity-based applications and services represent a fast growing social and technological trend that may have a major impact on the evolution of cellular wireless/mobile broadband technologies. These services are based on the awareness that at least two devices or two users are close to each other and, thus, may be able to directly communicate with each other.

Proximity-based applications include social networking, mobile commerce, advertisement, gaming, etc. These services and applications stimulate the design and development of a new type of device-to-device (D2D) communication that ideally are to be seamlessly integrated into current and next generation mobile broadband networks such as LTE (short for long-term evolution) and LTE-advanced. By leveraging direct connectivity between two devices in the network, D2D communication would enable machines to communicate directly with one another.

The existing mobile broadband networks are designed to optimize performance mainly for network-based communications and thus are not optimized for D2D-specific requirements. For instance, they do not support the establishment of direct links between two devices. The efficient support and seamless integration of D2D communication in current and future mobile broadband technologies requires enhancements or modifications across different layers, e.g., physical (PHY) and MAC layers, in order to optimally address the future D2D demands, meet performance requirements, and overcome technical challenges.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this document will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views, unless otherwise specified.

FIG. 1 is a block diagram of a wireless neighborhood having mesh, multi-hop, D2D broadcasting, and spatial reuse, according to some embodiments;

FIG. 2 is a diagram showing possible discovery signals that may employ the D2D discovery signal transmission method of FIG. 2, according to some embodiments;

FIG. 3 is a signaling diagram of a D2D discovery signal method, according to some embodiments;

FIG. 4 is a diagram illustrating how temporary identifiers can be used to configure user equipment to transmit and/or monitor D2D transmissions under the D2D discovery signal method of FIG. 3, according to some embodiments;

FIG. 5A-5C are flow diagrams illustrating three ways to activate and deactivate a discovery signal for transmission using the D2D discovery signal method of FIG. 3, according to some embodiments;

FIGS. 6A-6F are flow diagrams illustrating six examples of the D2D discovery signal method of FIG. 3, according to some embodiments;

FIG. 7 is a flow diagram illustrating another example of using the D2D discovery signal method of FIG. 3 with one or more D2D groups, according to some embodiments;

FIG. 8 is a flow diagram illustrating another example of using the D2D discovery signal method of FIG. 3 with one or more D2D groups, according to some embodiments;

FIG. 9 is a sample downlink control information bitmap used by the D2D discovery signal method of FIG. 8, according to some embodiments;

FIGS. 10A and 10B are two simplified diagrams showing how the D2D discovery signal method 200 is operated, according to some embodiments; and

FIG. 11 is a simplified diagram showing a system in which the D2D discovery signal method 200 is operated, according to some embodiments.

DETAILED DESCRIPTION

In accordance with the embodiments described herein, a method to transmit and receive a device-to-device (D2D) discovery signal is disclosed. The D2D discovery signal method operates using currently defined discovery signals as well as novel discovery signals, such as discovery signals employing a PUCCH-based uplink signal, an SRS-based demodulation and reference signal, or a single tone-based beacon signal. Under the D2D discovery signal method, an enhanced base station (eNB) configures the D2D discovery signal to both the transmitter (TX) user equipment (UE) and the receiver (RX) UE, then activates the D2D discovery signal to the TX and RX UEs, such that D2D signal transmission can thereafter occur from either the eNB or the TX UE, and monitored by the RX UE. Once the eNB deactivates the D2D discovery signal, D2D transmissions between UEs cease. Transmissions to configure, activate, and deactivate the D2D discovery signal can be unicast, multicast, or broadcast.

In the following detailed description, reference is made to the accompanying drawings, which show by way of illustration specific embodiments in which the subject matter described herein may be practiced. However, it is to be understood that other embodiments will become apparent to those of ordinary skill in the art upon reading this disclosure. The following detailed description is, therefore, not to be construed in a limiting sense, as the scope of the subject matter is defined by the claims.

FIG. 1 is a simplified diagram of a wireless neighborhood 100 consisting of a single macro eNB 20A, two pico eNBs 20B and 20C (collectively, “eNBs 20”), and UEs 50A-50T (collectively, “UEs 50”), according to some embodiments. The UEs 50 are depicted as cellular phones, but could just as easily be laptop computers, smartphones, or other wireless devices. Four of the UEs 50A-50D are shown larger than the other UEs, and operate as D2D coordinators for other locally disposed UEs.

The wireless neighborhood 100 consists of five D2D clusters 40A-40E (collectively, “D2D clusters 40”). The first D2D cluster 40A includes the D2D coordinator UE 50B along with two regular UEs 50 forming a D2D unicast link between UE 50D and UE 50E. The D2D coordinator UE 50B can further communicate with a pico/home eNB 20B.

The second D2D cluster 40B includes D2D coordinator 50D also communicating with pico/home eNB 20B. A D2D unicast link is formed between UEs 50F and 50G.

The third D2D cluster 40C features D2D coordinator 50C, communicating with macro eNB 20A, and D2D broadcast links between the D2D coordinator and each of UEs 50H and 50J. The transmissions in the D2D cluster 40C represent D2D broadcasting operations, in which the D2D coordinator broadcasts to both the UE 50H and the UE 50J simultaneously.

The fourth D2D cluster 40D features D2D coordinator 50A communicating with pico/home eNB 20C, and communicating with UE 50K, which then communicates with UE 50L. The operations taking place in the fourth D2D cluster 40D are known as a multi-hop configuration.

The fifth D2D cluster 40E does not include a D2D coordinator. Instead, UE 50N communicates directly with macro eNB 20A and a mesh configuration is established between UEs 50M, 50N, 50O, and 50P such that each is able to communicate with other UEs in the D2D cluster 50E.

In addition to the five clusters 40, the wireless neighborhood 100 features two rogue UEs 50T and 50S, each of which communicate directly with the macro eNB 20A.

D2D users may operate in a co-existing mode and reuse the spectrum with other cellular users (as shown in FIG. 1). Unlike the existing traditional LTE network infrastructure, D2D UEs 50 do not necessarily need to communicate via the central coordinator, the base station (eNB) 20. The D2D users 50 can communicate directly with each other or through hops of other D2D users. When D2D communication shares the same resources with the mobile broadband system, certain functions can still be controlled and coordinated by the eNodeB of the mobile broadband network in the case centralized control offers more benefits.

The proximity sensing methods may be implemented by the network through monitoring the UE attachment/association to a particular cell or using location-based services and protocols. In addition to these traditional methods, new proximity-based functionality may be added to the functions of the D2D coordinator. For instance, a special device discovery zone may be allocated in the D2D transmission region where device discovery signaling is used to assist in D2D cluster organization and D2D link establishment. A special discovery signal transmission interval can be introduced in the D2D transmission region for that purpose. Additionally, proximity sensing may be based on D2D link quality measurements.

As a discovery signal, the existing signal or newly defined signal can be used. FIG. 2 illustrates the possible discovery signals supported by the D2D discovery signal method, in some embodiments. Any of several different uplink signal/channel can operate as a discovery signal, such as a sounding reference signal (SRS) 70, a physical uplink control channel (PUCCH) uplink signal 72 (format 1/1a/1b/2/2a/2b/3), a demodulation-reference (DM-RS) signal 74, a physical uplink shared channel (PUSCH) uplink signal 76, an SRS/DM-RS-based uplink signal 78, a single tone-based beacon signal 90, and so on.

FIG. 3 is a signal exchange diagram illustrating operations performed by the D2D discovery signal method 200, according to some embodiments. The D2D discovery signal method 200 provides the methods for transmitting and receiving a D2D discovery signal. Here, the D2D discovery signal can be any of several types of signals, as enumerated in FIG. 2.

The signal exchanges of FIG. 3 are depicted in nine steps. Steps 1 and 2 pertain to configuration; steps 3 and 4 pertain to activation; steps 5, 6, and 7 pertain to D2D signal transmissions and receptions; steps 8 and 9 pertain to deactivation. The steps shown may be taken out of the order shown in FIG. 3, and, in some cases, the operations may occur simultaneously.

The signal exchanges in FIG. 3 occur between a base station, whether a macro eNB or a pico eNB 20, and two UEs 50W and 50X. The UEs 50W and 50X may be any of the UEs 50 depicted in FIG. 1. Before D2D transmissions can flow between UEs 50, independent of eNBs, the eNB 20 performs configuration of the D2D discovery signal followed by activation. Thus, in a first step, the eNB 20 configures the discovery signal for periodicity, offset, resource, used sequences, etc. In FIG. 2, the eNB 20 configures the D2D discovery signal for periodicity, offset, resource, used sequences, etc., for the UE 50W (step 1); then the eNB configures the D2D discovery signal for periodicity, offset, resource, etc., for the UE 50X (step 2).

The signal transmissions depicted in FIG. 3 between the eNB 20 and the UEs 50 may consist of unicast, multicast, or broadcast transmissions. Thus, the configuration steps depicted as first, a transmission from the eNB 20 to the UE 50W and then, a transmission from the eNB to the UE 50X, could take place together. The same is true for the activation and deactivation steps.

Following configuration, the eNB activates the D2D discovery signal for transmission. In FIG. 2, the eNB 20 separately configures the UE 50W and the UE 50X before D2D transmissions are possible. The UE 50W is activated for transmission (step 3) while the UE 50X is activated for reception (monitoring) (step 4). Again, the activation steps can take place out of order or together. In some embodiments, the activation step may be unicast, multicast, or broadcast to the UEs 50 in the wireless neighborhood.

As used herein, the term, “activate,” means the D2D discovery signal from a UE may be transmitted and/or that by another UE may be monitored (received). Likewise, the term, “deactivate,” means the transmission and/or reception of the D2D discovery signal may be terminated. Usually, the latter, deactivation, occurs to save power consumption of the UE 50.

Once the configuration and activation has been completed, D2D transmissions between UEs 50 are possible. D2D transmissions may also come from the eNBs 20. In FIG. 3, a D2D signal transmission takes place from UE 50W (transmitter) to UE 50X (receiver) (step 5). Further, a D2D signal transmission takes place from eNB 20 to UE 50X (receiver) (step 6), and a second D2D signal transmission takes place from eNB 20 to UE 50W (step 7).

A given UE 50 may be configured for half-duplex mode. This would mean that the UE 50 is able to transmit or receive (monitor), but would not be able to simultaneoulsy transmit and receive. Or, the UE 50 may be an advanced transceiver having full-duplex capability to both transmit and receive simultaneously. One objective of D2D transmissions is for transmissions to take place directly between UEs 50. Thus, where UE 50W is configured for half-duplex mode, the transmission in step 7, from eNB 20 to UE 50W would not take place since UE 50W was configured for transmission (step 3).

In some embodiments, the eNB 20 indicates which UEs are for transmission and which are for reception (monitoring) in a single step, such as by defining the bits where each is mapped to each UE in the wireless neighborhood, whereby a “0” in the bit location indicates that the UE mapped to that bit is a transmitter/receiver and a “1” in the bit location indicates the UE mapped to that bit is a receiver/transmitter. The bit fields may be conveyed in the format of L1 control signaling (e.g. PDCCH or EPDCCH). In another embodiment, two different fields are used, one to indicate those UEs performing D2D transmission operations and another to indicate those UEs monitoring D2D transmissions.

Radio network temporary identifiers (RNTIs) are used to scramble the code words, in the physical channel, prior to transmission on the physical channel. This scrambling process in the physical layer happens before modulation.

The Radio Network Temporary Identifier (RNTI) is a generic form of an identifier for a UE mainly when RRC connection exists. Some RNTIs, such as MBMS RNTI (M-RNTI), Paging RNTI (P-RNTI), and System Information RNTI (SI-RNTI), do not require an RRC connection and thus they have their own fixed values for each RNTI. For instance, in hexa-decimal expressions, M-RNTI, P-RNTI, and SI-RNTI may have the fixed values of FFFD, FFFE, and FFFF, respectively. RNTIs of several different types are used: Semi-Persistent Scheduling RNTI (SPS-RNTI), Cell RNTI (C-RNTI), MBMS RNTI (M-RNTI), Temporarily C-RNTI (TC-RNTI), Paging RNTI (P-RNTI), Random Access RNTI (RA-RNTI), Transmit Power Control-Physical Uplink Control Channel-RNTI (TPC-PUCCH-RNTI), and Transmit Power Control-Physical Uplink Shared Channel-RNTI (TPC-PUSCH-RNTI), to name a few. In this regard, D-RNTI may be newly defined and can represent a D2D group identifier used in D2D communications.

According to the 3GPP 36.321 specification, the C-RNTI is a 16-bit numeric value that is is part of the MAC logical channel group ID field (LCG ID). The C-RNTI thus defines unambiguously which data sent in a downlink direction within a particular long-term evolution (LTE) cell belongs to a particular subscriber. Thus, C-RNTI is used for cell tracing. The C-RNTI comes in three different flavors: temp C-RNTI, semi-persistent scheduling C-RNTI, and C-RNTI. A newly defined RNTI for D2D discovery and communication is denoted D-RNTI. Further, a D-RNTI may represent a group ID comprising multiple UEs.

In some embodiments, the UE identifiers may be represented using C-RNTIs and D-RNTIs, with the C-RNTI indicating an individual UE and D-RNTI indicating a group consisting of multiple UEs. Table 1 provides four different scenarios for defining two different UE IDs using C-RNTI and D-RNTI, according to some embodiments. Here, “UE#0” is meant to indicate a UE or a UE within a D2D group set up for D2D transmission/monitoring while “UE#1” indicates a UE or a UE within a D2D group set up for D2D monitoring/transmission, respectively. In the first choice, only C-RNTI, C-RNTI#0 for UE#0 and C-RNTI#1 for UE#1, is used. Since C-RNTI references a single UE 50, the first choice configures one UE for transmission and one UE for monitoring. In the fourth choice, only D-RNTI, D-RNTI#0 for UE#0 and D-RNTI#1 for UE#1, is used. Since D-RNTI references a D2D group of UEs, the fourth choice configures a UE 50 within a D2D group for transmission and another UE within another D2D group for reception.

In a special case, D-RNTI#0 may be identical to D-RNTI#1. This case can configure a UE 50 within a D2D group for transmission and another UE within the D2D group for reception. The second and third choices mix up use of the C-RNTI and D-RNTI, and thus envision single-transmitter-multiple-receiver and single-receiver-multiple-transmitter scenarios.

TABLE 1 Using RNTIs for D2D discovery user 1^(st) choice 2^(nd) choice 3^(rd) choice 4^(th) choice UE#0 C-RNTI#0 C-RNTI#0 D-RNTI#0 D-RNTI#0 UE#1 C-RNTI#1 D-RNTI#0 C-RNTI#0 D-RNTI#1

Thus, the operations depicted in the signaling diagram of FIG. 3 can be performed using these temporary identifiers. For example, when terminating the transmission/reception of the D2D discovery signal may be by the deactivation process, the deactivation may use the same RNTI (UE ID) as activation for cyclic redundancy check (CRC) scrambling (masking). In some embodiments, a further predefined field (e.g., all zero bits in a previously unused field) is used to indicate activation (or deactivation). In other embodiments, activation and deactivation use different RNTIs for CRC masking, thus making the predefined field unnecessary.

Further, for the above embodiment, the following procedures may be taken into account:

The eNB may configure D2D discovery signal to one or more UEs. FIG. 4 is used to illustrate how the eNB 20 may configure the D2D discovery signal to one or more UEs. Here, UE ID#0 denotes that UEs 0, 3, 7, and 9 are D2D transmitters while UE ID#1 denotes that UEs 1, 2, 4, 5, 6, and 8 are D2D receivers (monitors). In some embodiments, the UE ID#1 and the UE ID#2 are programmed using one or more of the RNTIs described above.

The eNB may configure one or multiple RNTIs to the UEs. FIG. 4 shows that, to configure the D2D discovery signal, the eNB may set up some UEs 50 to be transmitters and some UEs to be receivers (monitors), in some embodiments.

The eNB may activate the D2D discovery signal to one or more UEs 50. FIGS. 5A-5C are flow diagrams illustrating activation of the D2D discovery signal, according to some embodiments.

In a first embodiment (FIG. 5A), the activation is done by DCI (downlink control information) using PDCCH/EPDCCH (physical dedicated control channel/enhanced physical dedicated control channel) from the eNB 20 to the UEs 50 (block 202). The DCI may contain one or multiple RNTIs, and the CRC of the DCI may be masked by the identifier indicating the selected transmitters (RNTI#0) (block 204). The DCI may further convey one or multiple RNTIs (e.g., multiple C-RNTIs or a single identifier denoting multiple selected receivers, RNTI#1) (block 206). The RNTIs represent which UEs need to transmit or receive the D2D discovery signal. Following the D2D communications, the eNB 20 has the option to deactivate the D2D discovery signal.

In another embodiment, as illustrated in FIG. 5B, the network activates and deactivates the D2D discovery signal transmission/reception for one UE by sending the activation/deactivation MAC control element, either to the UE 50 or to a group of UEs (block 302). Once activated, transmission or monitoring by a single UE 50 is possible (block 304). Following the D2D communications, the eNB may deactivate the D2D discovery signal, also using the MAC control element

In still another embodiment, as illustrated in FIG. 5C, the eNB 20 sends activation RRC signalling (block 402). As with the MAC control element example, transmission or monitoring by a single UE 50 is possible (block 404). Following the D2D communications, the eNB may deactivate the D2D discovery signal, also using the RRC signaling.

FIGS. 6A-6F provide six examples for programming RNTIs so that D2D transmissions can take place, in some embodiments.

EXAMPLE 1

In the first example, groups of UEs 50 will be transmitters and groups of UEs will be monitors. Thus, D-RNTI, the temporary identifier useful for D2D group transmissions, is used. As illustrated in FIG. 6A, the temporary identifier D-RNTI#0 can be used to indicate the UEs 50 within a D2D group which may transmit the D2D discovery signal (block 502). Similarly, D-RNTI#1 can be used to indicate the UEs within a D2D group which may monitor the D2D discovery signal (block 504).

EXAMPLE 2

This example is simply the opposite of example 1, in that the programming of transmitters and monitors is reversed. As illustrated in FIG. 6B, D-RNTI#0 indicates the UEs within a D2D group which may monitor the D2D discovery signal (block 602). D-RNTI#1 indicates the UEs within a D2D group which may transmit the D2D discovery signal (block 604).

EXAMPLE 3

Where a single transmitter or a single receiver are to be programmed, the temporary identifier, C-RNTI, can be used. As illustrated in FIG. 6C, a single transmitter and a single receiver are being set up. C-RNTI#0 indicates the UE for transmitting the D2D discovery signal (block 702). C-RNTI#1 indicates the UE for monitoring the D2D discovery signal (block 704).

EXAMPLE 4

This example is simply the opposite of example 3, in that the programming of the single transmitter and the single monitor are reversed. As illustrated in FIG. 6D, C-RNTI#0 indicates the UE for monitoring the D2D discovery signal (block 802). C-RNTI#1 indicates the UE for transmitting the D2D discovery signal (block 804).

EXAMPLE 5

This example is for multiple transmitters but a single receiver. As illustrated in FIG. 6E, D-RNTI#0 indicates the UEs within a D2D group which may transmit the D2D discovery signal (block 902). C-RNTI#0 indicates the UE which may monitor the D2D discovery signal (block 904).

EXAMPLE 6

This example is for a single transmitter but multiple receivers. As illustrated in FIG. 6F, C-RNTI#0 indicates the UE which may transmit the D2D discovery signal (block 1002). D-RNTI#0 indicates the UEs within a D2D group which may monitor the D2D discovery signal (block 1004).

In other embodiments, the activation/deactivation of D2D discovery signal may be done by group indication. FIGS. 7 and 8 are two flow diagrams in which one or more D2D groups are activated for D2D discovery. FIG. 7 pertains to wireless neighborhoods in which one D2D group acts as D2D transmitters and another D2D group acts as D2D monitors. FIG. 8 pertains to wireless neighborhoods in which some UEs within a single D2D group act as transmitters while other UEs in the same D2D group are monitors.

In FIG. 7, the eNB 20 configures the D2D discovery signal (block 1102), using the techniques described above. Thereafter, one or more D2D groups, each group consisting of one or more UEs 50, are configured (block 1104). Each D2D group may have its own D-RNTI. For example, D2D group #0 is configured with D-RNTI#0, consisting of UE#0, #1, . . . , #N-1; D2D group #1 is configured with D-RNTI#1 consisting of UE#N, . . . , #M-b 1; and so on (blocks 1106A-C).

A DCI with CRC masked by a first D-RNTI indicates which UEs 50 are to be transmitters (block 1108) and which UEs are to be monitors of the D2D discovery signal in a given configuration.

FIG. 8 illustrates a second configuration in which the DCI contains a bit field to indicate both transmission and monitoring of the D2D discovery signal. This procedure may be used when the UEs 50 for transmission are part of the same D2D group as the UEs for monitoring.

In FIG. 8, the eNB configures the D2D discovery signal (block 1202), as described above. One or more D2D groups consisting of one or more UEs is configured, each with its own D-RNTI (block 1204). Individual D2D groups are configured as before (blocks 1206A-C). In this case, the UEs 50 for transmission and the UEs for monitoring are from the same group. Thus, in some embodiments, the DCI size is the number of UEs in the D2D group from which the transmitters and monitors are to be configured. The bitmap of the DCI indicates which UEs 50 are transmitters and which UEs are monitors.

FIG. 9 provides one possible implementation of the bitmap, according to some embodiments. Each bit may represent transmission or reception (monitoring). “1” may represent that the corresponding UE 50 is to transmit the D2D discovery signal, while “0” may represent that the corresponding UE needs to monitor the D2D discovery signal (or “0” for transmission and “1” for reception).

Each bit position may be occupied by each UE within a D2D group. For example, the D2D group with D-RNTI#0 from FIG. 8 (block 1206A) includes UE#0, #1, . . . , #9. Therefore, the size of the DCI for indicating transmission/reception of D2D discovery signal is 10, which is the number of UEs in that D2D group. The first bit may be for UE#0, the second bit may be for UE#1, and so on.

FIG. 10A is a simplified block diagram of a wireless neighborhood 400 including the eNB 20 and the UE 50, both of which are transceivers. The eNB 20 and the UE 50 employ the above-described D2D discovery signal method 200, according to some embodiments. In this example, the eNB 20 operates as a transmitter and the UE 50 operates as a receiver.

Each device includes an antenna 154, a front-end 132, a radio 136, a baseband digital signal processor (DSP) 138, and a medium access controller (MAC) 130. Although both devices have the hardware shown in each device, the eNB 20 is shown having a power amplifier 146 in its front-end 132 while the UE 50 includes a low noise amplifier 148 in its front-end. The eNB 50 includes a digital-to-analog converter (DAC) 134 while the UE 50 includes an analog-to-digital converter (ADC) 142. The UE 50 may be virtually any wireless device, such as a laptop computer, a cellular phone, or other wireless system, and may operate as a transmitter (transmit mode) or as a receiver (receive mode).

The MAC 130 includes an embedded central processing unit (CPU) 124 and a data memory 120, such that the D2D discovery signal method 200, some portion of which is software-based, in some embodiments, may be loaded into the memory and executed by the CPU. The depiction of FIG. 10A is a simplified representation of the MAC 130, and other devices, circuits, and logic elements that may be part of the MAC are omitted.

The MAC 130 interfaces with logic devices that are commonly found in transmitters and receivers: the front-end 132, the DAC 134, the ADC 142, the radio 136, and the DSP 138. The devices 132, 134, 136, 138, and 142 are also known herein as target modules. The target modules, as well as the logic devices within the MAC 130, may consist of hardware, software, or a combination of hardware and software components.

The target modules are commonly found in most transmitters and receivers. The FE 132 is connected to the antenna 154, and includes a power amplifier (PA) (for the transmitter), a low noise amplifier (LNA) (for the receiver), and an antenna switch (not shown), for switching between transmitter and receiver modes. The DAC 134 is used to convert the digital signal coming from the DSP 138 to an analog signal prior to transmission via the radio (transmitter); conversely, the ADC 142 is used to convert the analog signal coming from the radio to a digital signal before processing by the DSP 138 (receiver). At the eNB 20, the radio 136 transfers the signal from base-band to the carrier frequency; at the UE 50, the radio 136 transfers the signal from carrier frequency to base-band. At the UE 50, the DSP 138 demodulates the OFDM signal from the ADC 142, for processing by the MAC 130. At the eNB 20, the DSP 138 modulates the MAC data into an OFDM signal in base-band frequency, and sends the resulting signal to the DAC 134.

A typical transmit operation occurs as follows: at the eNB 20, the MAC 130 sends a packet to the DSP 138. The DSP 138 converts the packet into a digital OFDM signal and sends it to the DAC 134. The DAC 134 converts the signal into an analog signal, and sends the signal to the radio 136. The radio 136 modulates the base-band signal to the carrier frequency and sends the signal to the power amplifier 146 of the front-end 132, which amplifies the signal to be suitable for over-air transmission via the antenna 154.

At the UE 50, the signal is received by the antenna 154. The weak analog signal is received into the low noise amplifier 148 of the front-end 132, sending the amplified analog signal to the radio 136, which filters the signal according to the selected frequency band and demodulates the carrier frequency signal into a base-band signal. The radio 136 sends the analog signal to the ADC 142, which converts the analog signal to a digital signal, suitable for processing by the DSP 138. The DSP 138 demodulates the OFDM signal and converts the signal to MAC 130 packet bytes. Other operations, such as encryption and decryption of the packets, are not shown. Where the transmission is successful, the packet received by the MAC 130 in the UE 50 is the same as the packet transmitted by the MAC 130 in the eNB 20.

In other embodiments, as depicted in FIG. 10B, the eNB 20 and the UE 50 do not include a CPU 124 in the MAC 130. Instead, an application-specific integrated circuit (ASIC) 190 may drive the D2D discovery signal method 200 as a state machine implemented using logic registers (192). The ASIC solution of FIG. 10B may be preferred over the MAC-based implementation of FIG. 10A, for example, in systems in which low power consumption is important.

FIG. 11 is a simplified block diagram of a UE 50, according to some embodiments. The UE 50 executes the above-described D2D discovery signal method 200, according to some embodiments. The UE architecture includes a processing system 530 that can include one or more processors. The UE architecture further includes a memory 532 inside which an operating system 534 may be loaded, a storage module 544 for storing data 538, and an antenna system 540. Each device is connected by way of an interconnect 550 and powered by a power supply 536.

While the application has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention. 

We claim:
 1. A method comprising: configuring, by an enhanced base station (eNB), a device-to-device (D2D) discovery signal, by: transmitting a first configuring signal to a first user equipment (UE), wherein the first UE is to be a transmitter of D2D transmissions; transmitting a second configuring signal to a second UE, wherein the second UE is to be a monitor of D2D transmissions; activating, by the eNB, D2D signaling, by: transmitting a first activation signal to the first UE; and transmitting a second activation signal to the second UE; wherein the first UE performs a D2D transmission to the second UE without involvement of the eNB.
 2. The method of claim 1, further comprising: deactivating, by the eNB, D2D signaling, by: transmitting a first deactivation signal to the first UE; and transmitting a second deactivation signal to the second UE; wherein D2D transmissions between the first UE and the second UE cease.
 3. The method of claim 1, configuring, by the eNB, the D2D discovery signal further comprising: configuring a radio network temporary identifiers (RNTI) to the first UE; and configuring a second RNTI to the second UE.
 4. The method of claim 3, further comprising: configuring the RNTI to the first UE for periodicity, offset, resource, and used sequence; and configuring the second RNTI to the second UE for periodicity, offset, resource, and used sequence.
 5. The method of claim 1, activating, by the eNB, the D2D discovery signal further comprising: sending, by the eNB, a downlink control information (DCI) using a physical dedicated control channel (PDCCH) to the first UE and to the second UE, wherein the DCI: contains one or multiple radio network temporary identifiers (RNTIs) and a cyclic redundancy check (CRC) of the DCI is masked by a first RNTI, the first RNTI comprising UEs selected as transmitters of D2D signaling; and conveys a second RNTI comprising UEs selected as transmitters and monitors of D2D signaling.
 6. The method of claim 1, activating, by the eNB, the D2D discovery signal further comprising: sending, by the eNB, an activation medium access control (MAC) control element.
 7. The method of claim 1, activating, by the eNB, the D2D discovery signal further comprising: sending, by the eNB, an activation radio resource control (RRC) signaling.
 8. The method of claim 3, further comprising: configuring a cell-RNTI (C-RNTI) to the first UE; and configuring a second C-RNTI to the second UE.
 9. The method of claim 3, further comprising: configuring a D2D-RNTI (D-RNTI) to the first UE; and configuring a second D-RNTI to the second UE.
 10. The method of claim 3, further comprising: configuring a cell-RNTI (C-RNTI) to the first UE; and configuring a D2D-RNTI (D-RNTI) to the second UE.
 11. The method of claim 3, further comprising: configuring a D2D-RNTI (D-RNTI) to the first UE; and configuring a cell-RNTI (C-RNTI) to the second UE.
 12. An enhanced base station (eNB) comprising: an antenna; a front end coupled to the antenna; and logic to: transmit a first configuring signal to a first user equipment (UE), wherein the first UE is to be a transmitter of device-to-device (D2D) transmissions; transmit a second configuring signal to a second UE, wherein the second UE is to be a monitor of the D2D transmissions; transmit a first activation signal to the first UE; and transmit a second activation signal to the second UE; wherein succeeding D2D transmissions between the first UE and the second UE take place without involvement of the eNB.
 13. The eNB of claim 12, wherein the logic further: transmits a first deactivation signal to the first UE; and transmits a second deactivation signal to the second UE; wherein D2D transmissions between the first UE and the second UE cease.
 14. The eNB of claim 12, wherein the logic comprises a software program executed by a central processing unit in the eNB.
 15. The eNB of claim 12, wherein the logic comprises an application-specific integrated circuit driving a state machine implemented using logic registers.
 16. A user equipment (UE) comprising: an antenna; a front end coupled to the antenna; and logic to: receive a first configuring signal from an enhanced base station (eNB), wherein the configuration signal indicates that the UE is to be a transmitter of device-to-device (D2D) transmissions; receive a second configuring signal, wherein the second configuration signal indicates that a second UE is to be a monitor of the D2D transmissions; receive a first activation signal from the eNB; wherein the UE is thereafter capable of sending D2D transmissions to the second UE without further involvement of the eNB.
 17. The UE of claim 16, wherein the logic further: receives a deactivation signal from the eNB; wherein D2D transmissions between the first UE and the second UE cease.
 18. The UE of claim 16, wherein the logic comprises a software program executed by a central processing unit in the UE.
 19. The UE of claim 16, wherein the logic comprises an application-specific integrated circuit driving a state machine implemented using logic registers. 